If I was spending that sort of money then I'd have a Condor or a Mercian or possibly a Van Nicholas, but no need to spend more than about £550 on the frame, otherwise you won't have enough to to get a decent spec groupset or wheels.

If you are not wedded to steel, then a Kinesis TK2 with Tiagra/Veloce groupset would make a fine audax/light tourer.

I haven't worked it out, but on a large frame what would the extra 10mm layback be equivalent too, 1 degree shallower?

at 90cm saddle height one degree angle change is worth ~1.5cm of layback. So if we are to have seat posts (over 20mm layback) which allow for even one degree extra seat angle, we need at least 35mm layback. Two degrees extra and we need 50mm layback.

Right now there is limited choice in long layback seat pins and none that are 'commodity priced' around the £10 mark which may effectively deter people from experimentation.

stewartpratt wrote:.......Of course, the OP may well be a different shape to me and might be more flexible on seat angle. But a 72 seat plus caliper brakes and a 135mm rear end? I don't think such a frame exists.

135 oln MTB hubs not only have lower dishing but are better sealed from the elements than road hubs.I have a pair of Ultegra 6600 series that needed cones at 7,000miles after those and 105road hubs before them I'm glad I have a 132.5mm rear end on my Audax Mk3 Whilst used in worse conditions a pair of XT 756's that have yet to need anything other than a service occasionally with 20.000miles on them,

I didn't notice the steering geometry listed in there, but the photos don't seem to show anything too unusual-looking.

cheers

I don't know the steering angle on mine(which a medium/large) and heve never measured the fork offset * but it has lovely neutral handling and is comfortable for 100+miles rides.* I bought it from SJS as a Frameset and on the understanding that I had 100day return policy with no questions asked so thought I give it a go,I've never regreted the purchase:-

the head angle looks to be about 73 degrees. Can't be certain of the last 1/2degree because there is slight parallax in the picture (the line at the bottom is parallel to the wheel centre line, but doesn't sit at the bottom of both wheels).

Audax Mk 3 forks come in 43, 46, 50, 55mm offset according to SJS website http://www.sjscycles.co.uk/thorn-audax-mk3-1-1-8-inch-ahead-steel-fork-matt-black-prod27193/Head angle is not listed in their colourful pdf. , you have to read between the lines a bit...The small bike and the medium bike with a short top tube won't take a carbon fork, so guessing the carbon fork is 45mm offset....... I reckon the two short bikes have a shallow head angle and the long offset forks to get toe clearance at the same time as a short top tube.....that makes the rest not too far from 72/73 deg for 45mm offset. (or 43/46mm offset....anybody tell the difference?)Why not just publish the numbers?

Absolutely. That's the sole reason why Thorn have never been anywhere near a shortlist of mine: I'm not going to buy a bike if I don't know it's got the right geometry. Even though I have one of the Thorn Raven tandems and know that the build quality from their Taiwanese producer is the best I've ever seen from a factory-produced frame.

Looks a reasonable set of numbers above, though (even if a 595 top tube is shorter than I like - my Pacer is 605 and my CAAD9 600), but that fork looks eye-wateringly slim. My Pacer front end shimmies way, way more than I'd like and that fork looks twangier than the Pacer's and would surely would be worse. But then Thorn are a bit fundamentalist about a compliant front end; whereas I'd much rather a stiff and precise fork, preferably with a disc brake on the end of it (which is what I intend doing with the Pacer).

Last edited by stewartpratt on 24 Nov 2012, 9:30pm, edited 1 time in total.

stewartpratt wrote:Absolutely. That's the sole reason why Thorn have never been anywhere near a shortlist of mine: I'm not going to buy a bike if I don't know it's got the right geometry.

But you've not ridden a Mk3 right?As I said with 100day money back guarrentee i wasn't complaining,I was complaining even less when I rode it .

Even though I have one of the Thorn Raven tandems and know that the build quality from their Taiwanese producer is the best I've ever seen from a factory-produced frame

.I'm glad we agree

My Pacer front end shimmies way, way more than I'd like and that fork looks twangier than the Pacer's and would surely would be worse. But then Thorn are a bit fundamentalist about a compliant front end; whereas I'd much rather a stiff and precise fork, preferably with a disc brake on the end of it (which is what I intend doing with the Pacer).

Can I reassure you that having had the Mk3's 72deg parallel,531 tubed predessor shimmey under certain circumstances and with certain tyres fitted,the Mk3 is definately more comfortable especially the fork,stiffer around the BB area and extremely well behaved and planted.I've done some 45mph+ decents on this bike on some pretty bummpy tarmac too,solid as a rock!If I had a complaint It'd be that the head tube could be a leettle higher so I needn't have as many spacers under the stem,but then again I do like my handlebars level with the saddle.

IMHO it is quite likely that larger frames especially can tend to shimmy simply because the main triangle of the frame isn't stiff enough in torsion. This is quite likely if the frame design uses the same tube diameters and gauges in medium and large sizes; the larger frames just get less and less stiff as they get larger and larger.

With a 1" steerer, steerer flex is very noticable espcially in larger sizes, but this effect is somewhat reduced with 1 1/8" steerer forks. The fork blades can flex mostly in the middle/middle upper section if the tube gauge varies enough; the slim tips look nice but need to be very thin for a considerable length before they contribute greatly to the springiness of the fork; this is because the bending forces are rather small near the dropouts, but become much larger higher up.

I think R2 is right; it may be worth a go on one, if it fits you. It is the only way you'll find out if it rides how you want or not.

Haven't ridden the Thorn, no, for one simple reason: Other manufacturers publish their geometry online.

Problem is that I know exactly what geometry I want, and being at the extreme of off-the-peg sizing charts I have little or no room for negotiation on it. So whilst experience does count for more than numbers, Thorn's approach of hiding the geometry and having to order one and build it up to test it out doesn't really make sense for a customer like me.

in all fairness numbers are just that, numbers; they don't tell you everything. You can build two frames to the same geometry and same tube gauges and have them feel and ride rather different. And that is if they come out to dwg (which is not always the case). The reason for this is that you can cut single butted tubes anyway you like more or less, and double-butted tubes are usually available with different centre lengths, and few framebuilders publish the specs of their tube butts. Even if they did, you wouldn't know if they had actually adhered to them, or had perhaps mitred some tubes at the wrong ends if the butt lengths are unequal.

So a 0.8/0.5/0.8mm tube (say) can have bending properties that closely resemble either a 0.8 or a 0.5mm PG tube, and the torsional stiffness is a different matter again.

If you know what you want then a custom frame should be easy to specify. On the other hand if you think an off-the-peg might do then you should try one. If you can get yourself down to SJS they should be able to do a test ride I would have thought.

Absolutely: geometry tells you all about the fit but not everything about the ride characteristics. But the Pacer frameset was reduced to £240 so even though I knew it wasn't going to be as stiff as I would like, I knew it would fit me well until I can save up for an Indy Fab with oversized tubing

stewartpratt wrote:Haven't ridden the Thorn, no, for one simple reason: Other manufacturers publish their geometry online.

Problem is that I know exactly what geometry I want, and being at the extreme of off-the-peg sizing charts I have little or no room for negotiation on it. So whilst experience does count for more than numbers, Thorn's approach of hiding the geometry and having to order one and build it up to test it out doesn't really make sense for a customer like me.

Here's the full story.Having just discovered a spiral crack in my Raleigh's headtube and needed new frame,I decided to phone Mercian and ask about their off the peg Audax frames.I was told there wasn't really clearance for anything bigger than 25mm tyres at a pinch and a three week wait with a price tag of £595 inc vat.Next stop Bob Jackson to ask the same questions to be told what I needed (rather than me tell them what I wanted) in such an off hand manner it bordered on rude I hung up on them.Having had a Thorn tandem and liked the workmanship and ride,not to mention good service when I ordered stuff for it previously,I rang them about the Mk3.From the off I was put at ease with the promised 100day guarentee and the price at the time of £299+ £15 potage seemed a good deal too.I rang them on a Tuesday morning and was getting ready to go out on Wednesday morning as the frame arrived.It came with a BB fitted,a seatpost,FSA headset fitted,and every threaded bolt hole fitted with the appropriate stainless steel bolt and washer fitted.I've never looked back or regreted going to either of the other two makers.I can get along with everyone having their preferences,I've got mine you've got yours and I won't pull apart what I don't know about.